HOW TO COMPENSATE FOR PRESS BRAKE DEFLECTION
What is press brake deflection?
If you own a press brake that is eight feet or longer, chances are you've experienced press brake deflection. Press brake deflection is when the ram and bed flex under load. Most modern press brakes are powered by two hydraulic cylinders on either end and are supported by side frames, meaning that both the power and support are isolated to either end of the machine. This results in the machine being the strongest and most rigid at the two ends. As a result of this design, ram and bed deflection is a normal part of press brake operation. Ram and bed deflection occurs most dramatically in locations farthest away from the hydraulic cylinders; in other words, it is most noticeable in the middle of the press brake.
While press brake deflection is a natural occurrence in modern press brake operations, it can pose challenges to getting consistent bend angles, particularly across the entire length of long parts. Because the ram and bed deflect in the shape of an arc, the angle produced will be more obtuse in the center of the workpiece, or at the peak of the arc. For instance, imagine you are bending a 90° angle across the length of a 10 foot part. While
the ends of the finished part may be an accurate 90°, you could end up with as much as a 98° bend angle in the center. This phenomenon is known as the“canoe effect."
How to compensate for press brake deflection
There are a variety of methods used to compensate for press brake deflection, some of which are more effective than others.
1.Hydraulic crowning - Some press brakes come from the factory with hydraulic crowning already built in. Hydraulic crowning uses hydraulic cylinders located in the bed of the machine. As the cylinders are filled with hydraulic pressure, they exert an upward force on the bed of the machine to compensate for deflection. Modern hydraulic crowning systems often feature what is known as dynamic crowning. Dynamic crowning provides a
unique benefit of monitoring inconsistencies and resistance during the bending process, allowing for it to make real time adjustments to correct not only inconsistencies in the press brake but inconsistencies in the material as well.
2. Mechanical Crowning - By far the most common solution to compensating for deflection is mechanical crowning systems. Mechanical crowning systems are installed in place of a bottom tool holder, as they also serve this function. They typically feature either mechanical or hydraulic clamping as options. They also typically feature different drive designs, from analog to digital readouts and from hand crank assemblies to CNC motors. Mechanical crowning systems can typically be outfitted to the press brake at the time of purchase, as well as after the purchase in the form of a retrofit. Mechanical crowning systems vary in design, accuracy, and ease of use from product to product.
Mechanical Manual Crowning ( NC Press Brake) Mechanical Auto Crowning ( CNC Press Brake )